Downhole Outer Drill Bit

ABSTRACT

A downhole drill bit, of the type used to bore into the earth when searching for or extracting subterranean resources, may comprise a working face opposite an attachment end and an opening passing from the attachment end through to the working face. A protrusion on one end of a bottom hole assembly may extend through the opening and be exposed at the working face when the drill bit is attached to the end of the bottom hole assembly. In various embodiments the exposed portion of the protrusion may house conduits or nozzles for handling fluids; sensors, transmitters or wires for handling electrical signals; or mechanical hammers, motors or cutters for degrading an earthen formation. In this way, the protrusion may bring such elements from the bottom hole assembly to the working face of the drill bit.

BACKGROUND

When exploring for or extracting subterranean resources such as oil,gas, or geothermal energy, it is common to form boreholes in the earth.Such boreholes are often formed by suspending a specialized drill bitfrom a derrick or offshore platform and rotating the drill bit to engageand degrade the earth as it turns. The drill bit may be suspended bycoiled tubing or a series of drill pipe sections connected end to end toform a drill string, and rotated at the derrick/platform or by adownhole motor disposed towards an end of the drill string. If a drillbit becomes dull or damaged it may cease to drill efficiently and mayneed to be replaced before drilling continues.

In many situations, it may be desirable to gain access to the drill bitas it drills. For example, it may be desirable to discharge drillingfluid flowing through a drill string at a drill bit. This may be done tocool, clean or lubricate the drill bit or carry debris created by thedrill bit engaging an earthen formation up a borehole. In anotherexample, it may be desirable to place sensors at a drill bit as itdrills. This may be done to gather information about the formation beingdrilled as far in front of the drill bit as possible or to get the mostaccurate possible measurements of how the drilling process isprogressing. These sensors may measure natural conditions of an earthenformation or responses to energy transmitted into a formation fromtransmitters also disposed at the drill bit. In yet another example, itmay be desirable to control a trajectory of a drill bit as it bores intoa formation by manipulating degradation of the formation at the drillbit. This may be accomplished, for example, by placing cutters on anoffset mechanical hammer or rotational motor exposed at a drill bit andactivating it alternatingly as the drill bit rotates.

While placing these types of equipment as close to the drill bit aspossible may be desirable, placing them on the drill bit may becomeprohibitively expensive as drill bits may need to be replaced regularly,if not frequently. Accordingly, tools providing access to a drill bitthat need not be replaced as often as drill bits may be valuable.

BRIEF DESCRIPTION

A downhole drill bit may comprise a working face, capable of engagingand degrading tough earthen formations, opposite an attachment end,fashioned to attach to a bottom hole assembly. The drill bit may furthercomprise an opening passing from the attachment end through to theworking face. A protrusion on one end of a bottom hole assembly mayextend through the opening and be exposed at the working face when thedrill bit is attached to the end of the bottom hole assembly. Thisexposed portion of the protrusion may provide access for equipmenthoused within the bottom hole assembly to the working face whiledrilling. For example, in various embodiments, the protrusion mayaccommodate conduits or nozzles for handling fluids; sensors,transmitters or wires for handling electrical signals; or mechanicalhammers, motors or cutters for degrading an earthen formation. In suchconfigurations, the drill bit may be replaced when dull or damagedwithout requiring replacement of this additional equipment.

DRAWINGS

FIG. 1 is an orthogonal view of an embodiment of a drilling operationcomprising a drill bit secured to an end of a drill string suspendedfrom a derrick.

FIG. 2 is a perspective view of an embodiment of a bottom hole assemblycomprising a protrusion on one end thereof and a drill bit capable ofattachment to the end of the bottom hole assembly.

FIG. 3 is a perspective view of the embodiment of the drill bit shown inFIG. 2 attached to the end of the bottom hole assembly such that theprotrusion extends through an opening in the drill bit.

FIG. 4 is an orthogonal face view of an embodiment of a drill bit with aprotrusion extending through an opening therein and an exposed portionof the protrusion comprising a generally circular exposed surface.

FIGS. 5-1, 5-2, 5-3 and 5-4 are longitude-sectional views of differentembodiments of bottom hole assemblies comprising various types ofequipment housed therein and exposed at a working face of a drill bit bya protrusion passing through an opening in the drill bit.

FIG. 6 is a perspective view of an embodiment of a bottom hole assemblycomprising a protrusion on one end thereof and a drill bit capable ofattachment to the end of the bottom hole assembly.

FIG. 7 is an orthogonal face view of the embodiment of the drill bitshown in FIG. 6 with the protrusion extending through an opening thereinand an exposed portion of the protrusion comprising a generallynon-circular exposed surface.

FIG. 8-1 is a longitude-sectional view of an embodiment of a bottom holeassembly comprising a protrusion with a periphery surface parallel witha central axis of the bottom hole assembly. The protrusion is alignedwith a drill bit capable of attachment to the end of the bottom holeassembly.

FIG. 8-2 is a longitude-sectional view of the embodiment of the drillbit shown in FIG. 8-1 attached to the end of the bottom hole assemblywith a locking mechanism.

DETAILED DESCRIPTION

FIG. 1 shows an embodiment of a drilling operation comprising a drillstring 110 suspended from a derrick 112 into the earth 114. A bottomhole assembly 100 may be disposed adjacent a distal end of the drillstring 110 and comprise any of a number of mechanical, electrical, orfluid systems known in the art to aid in increasing rate of penetrationof drilling; steering; gathering, storing, or communicating data; orsensing. A drill bit 118 may be secured to the bottom hole assembly 100capable of engaging and degrading the earth 114 as it is rotated to forma borehole 116 allowing for the drill string 110 to advance. In manysituations, it may be desirable to position the various systems housedwithin the bottom hole assembly 100 as close to a working face of thedrill bit 118 as possible.

FIG. 2 shows an embodiment of a bottom hole assembly 200 comprising agenerally elongate shape. A protrusion 220 may be disposed on one end ofthe bottom hole assembly 200 and extend out therefrom. The protrusion220 may be attached to the bottom hole assembly 200 by a spider 228allowing drilling fluid traveling through the bottom hole assembly 200to pass the protrusion 220. In the embodiment shown, the protrusion 220extends from a threaded pin 227 comprising a generally circular crosssection surrounded by threads 221. The threaded pin 227 may be receivedby an attachment end 222 of a drill bit 218 comprising a threaded box(hidden). While the present embodiment comprises a threaded pin 227 andbox combination, other attachment mechanisms may be similarly suitable.A working face 223 may be disposed on the drill bit 218, opposite theattachment end 222, and comprise a plurality of cutters 224, formed atleast partially of superhard material (e.g. polycrystalline diamond),secured thereto. The working face 223 may also comprise a plurality ofblades 225 extending therefrom allowing the cutters 224 to dig into aformation to be degraded and debris generated during the degradation toexit through spaces between each of the blades 225. Additionally, anopening 226 may pass completely through the drill bit 218 from theworking face 223 to the attachment end 222.

FIG. 3 shows the embodiment of the drill bit 218, shown in FIG. 2,attached to the end of the bottom hole assembly 200. When attached, theprotrusion 220 may extend through the opening 226 passing through thedrill bit 218 to be exposed at the working face 223. In the embodimentshown, an exposed portion 330 of the protrusion 220 comprises agenerally circular exposed surface. The exposed portion 330 may also begenerally flush with the working face 223.

FIG. 4 shows an exposed portion 430 of a protrusion 420 surrounded by aworking face 423 of a drill bit 418. At least one cutter 444, comprisingsuperhard material (e.g. polycrystalline diamond), may be disposed onthe exposed portion 430 of the protrusion 420. In the embodiment shown,the cutter 444 is positioned within an organized pattern, such as alonga blade, with some of the plurality of cutters 424 disposed on theworking face 423. As the drill bit 418 is rotated, those of theplurality of cutters 424 positioned closer to an exterior 441 of theworking face 423 may travel at a higher speed relative to a formationbeing degraded, due to an increased radius, than cutters 424 positionedcloser to an axis of rotation 442 of the drill bit 418. Because of thishigher speed, cutters 424 positioned closer to the exterior 441 may bemore likely to receive wear or damage than those positioned closer tothe axis of rotation 442. When worn or damaged, the drill bit 418 may bereplaced. However, any equipment exposed at the working face 423 throughthe protrusion 420, which is also less likely to receive wear due to itsposition closer to the axis of rotation 442, may be left in place.

One example of equipment that may be housed within a bottom holeassembly and exposed at a working face of a drill bit by a protrusionpassing through an opening in the drill bit is fluid handling equipmentas shown in FIG. 5-1. Specifically, FIG. 5-1 shows drilling fluid 550-1traveling through a hollow center of a bottom hole assembly 500-1. Aconduit 551, passing through a protrusion 520-1 extending from thebottom hole assembly 500-1, may channel a portion of the drilling fluid550-1 to a nozzle 552, secured on an exposed portion 530-1 of theprotrusion 520-1, where it may be discharged at a working face 523-1 ofa drill bit 518-1. The drill bit 518-1 may be replaced when worn ordamaged without affecting the fluid flow path.

Another example of equipment that may be exposed at a working face by aprotrusion is electrical equipment as shown in FIG. 5-2. In the exampleshown, wires 553 may pass through a protrusion 520-2 and transmitelectrical signals to and from a transmitter 554 and a sensor 555positioned on an exposed portion 530-2 of the protrusion 520-2 at aworking face 523-2 of a drill bit 518-2. The transmitter 554 may sendenergy in any of a variety of forms, such as for example a magneticfield or gamma rays, into a formation being drilled that may reflect offof the formation, be altered by the formation or cause a reaction in theformation that may be sensed by the sensor 555. In alternateembodiments, a transmitter may not be necessary and a sensor alone, suchas for example an accelerometer or thermometer, may sense naturallyoccurring phenomena at a working face.

Yet other examples of equipment that may be exposed at a working face bya protrusion are extra degradation tools such as those shown in FIGS.5-3 and 5-4. For example, FIG. 5-3 shows at least one cutter 544-3extending from an end of an exposed portion 530-3 of a protrusion 520-3.The cutter 544-3 may be secured to a hammer mechanism 556 capable ofvibrating the cutter 544-3 for the purpose of increasing a rate ofpenetration of a drill bit 518-3, steering the drill bit 518-3, sendingan acoustic signal into a formation or for other reasons. In theembodiment shown, a motor 558-3 may actuate a valve 559-3 to alternatingroute drilling fluid 550-3 traveling through a hollow center of a bottomhole assembly 500-3 to the hammer mechanism 556 causing the cutter 544-3to extend and retract. In other embodiments, other types of hammermechanisms may achieve similar results.

In another example, FIG. 5-4 shows at least one cutter 544-4 extendingfrom an exposed portion 530-4 of a protrusion 520-4 and secured to amotor 557 capable of rotating the cutter 544-4 about an axis. Similar tothe hammer mechanism 556 shown in FIG. 5-3, the motor 557 may increase arate of penetration, steer, send signals into a formation or performother tasks. In the embodiment shown, the motor 557 comprises a rotor558-4 rotated relative to a stator 559-4 by a drilling fluid 550-4traveling through a hollow center of a bottom hole assembly 500-4.Rotation of the rotor 558-4 may be passed to the cutter 544-4 toincrease degradation of a formation. In other embodiments, other typesof rotational mechanisms may achieve similar results.

FIGS. 6 and 7 show an embodiment of a drill bit 618 that may be attachedto a bottom hole assembly 600 and allow a protrusion 620 of the bottomhole assembly 600 to pass through. An exposed portion 630 of theprotrusion 620 may comprise a non-circular shape. In order to fit thedrill bit 618 over the noncircular shape, the protrusion 620 maycomprise a periphery surface 661 parallel with a central axis 663 of thebottom hole assembly 600. The periphery surface 661 may extend from aboundary 662 of the exposed portion 630 at a working face 623 of thedrill bit 618 toward the bottom hole assembly 600.

The drill bit 618 may comprise a rotatable locking mechanism 667 tosecure the drill bit 618 to the bottom hole assembly 600. While arotatable locking mechanism 667 is shown in the present embodiment,other styles of locking mechanisms may achieve similar results. As alsoseen in this embodiment, the working face 623 may comprise at least onecutter 624 disposed encroaching on the boundary 662 of the noncircularexposed surface. It is believed that in some situations thisencroachment may aid in maintaining an organized pattern of cuttersbetween the exposed portion 630 of the protrusion 620 and the workingface 623. Some blades 625 extending from the working face 623 may alsocontinue uninterrupted onto the exposed portion 630 in an elevatedsection 664 of the exposed portion 630.

FIGS. 8-1 and 8-2 show an embodiment of a drill bit 718 comprising arotatable locking mechanism 767 that may secure the drill bit 718 to abottom hole assembly 700. The rotatable locking mechanism 767 may rotatefreely relative to a remainder of the drill bit 718 thanks to aplurality of ball bearings 770 secured within tracks 771. This relativerotation may permit the locking mechanism 767 to thread onto a threadedpin 727 of the bottom hole assembly 700 while allowing the remainder ofthe drill bit 718 to remain rotationally stationary relative to aprotrusion 720.

In the embodiment shown, the protrusion 720 is held onto the bottom holeassembly 700 by a removable retainer 772. Using such a removableretainer 772 for attachment may allow for simpler construction andeasier maintenance or replacement. For example, in the embodimentsshown, at least one snap ring may act as a removable retainer 772holding the protrusion 720 on the end of the bottom hole assembly 700.

Whereas the present invention has been described in particular relationto the drawings attached hereto, it should be understood that other andfurther modifications apart from those shown or suggested herein, may bemade within the scope and spirit of the present invention.

1. A downhole drilling assembly, comprising: a bottom hole assemblycomprising an elongate shape and a protrusion on an end thereof; and adrill bit comprising a working face opposite an attachment end and anopening passing from the working face to the attachment end; whereinwhen the attachment end of the drill bit is attached to the end of thebottom hole assembly the protrusion extends through the opening and isexposed at the working face.
 2. The downhole drilling assembly of claim1, wherein when the attachment end of the drill bit is attached to theend of the bottom hole assembly an exposed portion of the protrusion isgenerally flush with the working face.
 3. The downhole drilling assemblyof claim 2, wherein the working face comprises at least one bladeextending therefrom that continues on the exposed portion of theprotrusion.
 4. The downhole drilling assembly of claim 1, furthercomprising a conduit disposed within the protrusion allowing drillingfluid passing through the bottom hole assembly to exit at the workingface through an exposed portion of the protrusion.
 5. The downholedrilling assembly of claim 1, further comprising a wire disposed withinthe protrusion capable of communicating an electrical signal from thebottom hole assembly to an exposed portion of the protrusion at theworking face.
 6. The downhole drilling assembly of claim 1, furthercomprising a sensor disposed on an exposed portion of the protrusion atthe working face.
 7. The downhole drilling assembly of claim 1, furthercomprising a transmitter disposed on an exposed portion of theprotrusion at the working face.
 8. The downhole drilling assembly ofclaim 1, further comprising at least one cutter comprising superhardmaterial disposed on an exposed portion of the protrusion at the workingface.
 9. The downhole drilling assembly of claim 8, further comprising ahammer disposed within the bottom hole assembly capable of vibrating theat least one cutter.
 10. The downhole drilling assembly of claim 8,further comprising a motor disposed within the bottom hole assemblycapable of rotating the at least one cutter about an axis.
 11. Thedownhole drilling assembly of claim 8, wherein the cutter disposed onthe exposed portion of the protrusion is positioned within an organizedpattern with other cutters comprising superhard material disposed on theworking face.
 12. The downhole drilling assembly of claim 1, wherein theend of the bottom hole assembly comprises a threaded pin and theattachment end of the drill bit comprises a threaded box.
 13. Thedownhole drilling assembly of claim 12, wherein the protrusion issurrounded by threads of the threaded pin.
 14. The downhole drillingassembly of claim 12, wherein an exposed portion of the protrusioncomprises a generally circular exposed surface.
 15. The downholedrilling assembly of claim 1, wherein an exposed portion of theprotrusion comprises a noncircular exposed surface.
 16. The downholedrilling assembly of claim 15, wherein the protrusion comprises aperiphery surface extending from a boundary of the noncircular exposedsurface parallel with a central axis of the bottom hole assembly. 17.The downhole drilling assembly of claim 15, wherein the working facecomprises a cutter comprising superhard material disposed on the workingface and encroaching on a boundary of the noncircular exposed surface.18. The downhole drilling assembly of claim 1, further comprising aremovable retainer holding the protrusion on the end of the bottom holeassembly.
 19. The downhole drilling assembly of claim 18, wherein theremovable retainer comprises a snap ring.
 20. The downhole drillingassembly of claim 1, wherein the protrusion is attached to the bottomhole assembly by a spider allowing drilling fluid passing through thebottom hole assembly to pass the protrusion.